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Combating Climate Change with Ancient Aquaculture

Nature offers the best carbon storage technology the world has to offer.

Natural resources such as forests, grasslands, soil, oceans and other bodies of water naturally absorb and store carbon, serving as massive carbon sinks for our planet.

Optimizing these natural, passive processes offers the most efficient and cost-effective form of carbon storage. Planting a forest, for example, costs far less than building a farm of carbon-storing machinery, and it also offers a plethora of other positive environmental externalities.

For this reason, scientists have long studied these naturally occurring processes to learn about how we can take advantage of and even enhance them to meet global climate goals. Achieving the legally binding goals set out in the Paris agreement – which aims to limit global warming to 1.5º Celsius above pre-industrial averages – will not only require the rapid expansion of clean energy, but also major gains in removing the carbon that we’ve already put into the atmosphere, and then storing it somewhere that it would be causing further harm to the environment.
A new study shows that seaweed farms could be a promising solution to this challenge. A new study published this month in the scientific journal Nature Climate Change shows that seaweed farms can pull carbon out of the water around them and store it in the seabed below. When the carbon-rich plants die, they fall to the ocean floor and are quickly buried deeply, where they can hold on to that carbon for decades or even centuries. As a result, the study found that the amount of carbon stored under the seaweed farms was about twice as much as nearby sediment beds without seaweed farming operations.

The potential of seaweed farms to suck carbon out of seawater, another natural carbon sink, could be great news for the resilience of our oceans. As reported by phys.org, this phenomenon could “presumably allow the world’s oceans to absorb more atmospheric carbon without causing catastrophic side effects such as global coral die-offs.”

Not only could this have hugely positive implications for the carbon storage capacities of our oceans, the study also found that the technology only gets better with age. The study looked at 20 seaweed farms around the world with a wide range of ages and sizes, and found that older farms were able to absorb and store more carbon. Amazingly, the oldest farm included in the study has been operational for 300 years. The older farms were able to sequester up to 140 metric tons of carbon per hectare, making the seaweed farms as successful at carbon storage as ‘Blue Carbon habitats’ such as mangrove forests.

As luck would have it, seaweed aquaculture is already a booming industry. Today, the industry is a $16.7 billion market, with the lion’s share of production (about 80%) taking place in China and Indonesia. Not only does seaweed farming provide economic gains and food security – especially in Asian cultures where seaweed is a common part of the average diet – scientists are continually discovering more and more positive environmental externalities associated with the centuries-old practice.

According to the Nature Conservancy, “as it grows, seaweed absorbs nitrogen from the water, nitrogen that could otherwise contribute to the growth of algal blooms that gobble up oxygen and create ‘dead zones’ where other aquatic life can’t survive.” And now we know that along with all that nitrogen these farms are sucking up an extremely helpful amount of carbon as well.

However, the Nature Conservancy notes that “the sequestration potential of farmed seaweed is highly variable.” Since the seaweed is being grown for consumption in one way or another, the vast majority of farmed seaweed does not naturally decay and fall to the ocean floor, where it can sequester carbon in the seabed. Instead, that carbon is being cycled back out into the world.

 

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